Phenomena Relating to Charge in Insulators: Macroscopic Effects and Microscopic Causes

Conservation of current under steady-state conditions makes it possible to determine the sign of charges trapped in an insulator subjected to ionizing radiation. The maximum value of the surface potential can thus be estimated. On the basis of a given trapped charge distribution, the pattern of the electrical field and of the potential can thus be established, and the influence of the shape of the sample and its environment can be clearly shown. Change of trapped charges with time (at the start and after irradiation) is then examined. Finally, the microscopic causes of trapping of charge is suggested by analogy with semiconductors . Each stage is illustrated with examples and a number of practical consequences are deduced. To facilitate the understanding of the phenomena, this analysis begins with the better known macroscopic effects and works back to microscopic causes, which are often poorly controlled . Si nee the inverse process would be more logical, we have mentioned it in the conclusion, while pointing out some of the difficulties which arise

A targeted next-generation sequencing assay for the molecular diagnosis of genetic disorders with orodental involvement.

BACKGROUND: Orodental diseases include several clinically and genetically heterogeneous disorders that can present in isolation or as part of a genetic syndrome. Due to the vast number of genes implicated in these disorders, establishing a molecular diagnosis can be challenging. We aimed to develop a targeted next-generation sequencing (NGS) assay to diagnose mutations and potentially identify novel genes mutated in this group of disorders. METHODS: We designed an NGS gene panel that targets 585 known and candidate genes in orodental disease. We screened a cohort of 101 unrelated patients without a molecular diagnosis referred to the Reference Centre for Oro-Dental Manifestations of Rare Diseases, Strasbourg, France, for a variety of orodental disorders including isolated and syndromic amelogenesis imperfecta (AI), isolated and syndromic selective tooth agenesis (STHAG), isolated and syndromic dentinogenesis imperfecta, isolated dentin dysplasia, otodental dysplasia and primary failure of tooth eruption. RESULTS: We discovered 21 novel pathogenic variants and identified the causative mutation in 39 unrelated patients in known genes (overall diagnostic rate: 39%). Among the largest subcohorts of patients with isolated AI (50 unrelated patients) and isolated STHAG (21 unrelated patients), we had a definitive diagnosis in 14 (27%) and 15 cases (71%), respectively. Surprisingly, COL17A1 mutations accounted for the majority of autosomal-dominant AI cases. CONCLUSIONS: We have developed a novel targeted NGS assay for the efficient molecular diagnosis of a wide variety of orodental diseases. Furthermore, our panel will contribute to better understanding the contribution of these genes to orodental disease. TRIAL REGISTRATION NUMBERS: NCT01746121 and NCT02397824.journal articleresearch support, non-u.s. gov't2016 Feb2015 10 26importe

An expression for the Auger backscattering factor and the ϕ(0) function at oblique incidences

Based on simple physical arguments, the proposed analytical expression: $$describes the evolution as a function of the incident angle a, of the Auger backscattering factor r (= 1 + R) and of the ionization function of EPMA at the surface, ϕ(0). This expression leads to a new procedure of quantification in AES and EPMA by the measurement of the electron backscattering coefficient η via the measurement of electric current of the correctly polarized spécimen holder, which allows the local determination of r and ϕ(0) without the knowledge of the substrate composition. Its field of application concerns point analysis and images acquisition in Auger electron spectroscopy and X-ray emission spectroscopy with a special attention for the in-depth profiling by AES and the non destructive profilometry of coatings by EDS-EPMA. The results deduced from the proposed expression are in excellent agreement (at least for Uo ≥ 3) with the numerical values deduced from Monte Carlo simulations and from the solutions of the transport equation as proposed by other authors. Some aspects related to the influence of the roughness of the surface on the measurements are also indicated.Basée sur des arguments physiques simples, l'expression proposée:$$ rend compte analytiquement de l'évolution du coefficient de rétrodiffusion Auger r (= 1 + R) et de la fonction d'ionisation de l'EPMA à la surface ϕ(0), en fonction de l'angle d'incidence a des électrons. Elle conduit à une procédure inédite de quantification en AES et en EPMA, à savoir la mesure du coefficient de rétrodiffusion η via la mesure du courant du porte échantillon correctement polarisé pour déterminer localement r et ϕ(0) sans connaissance, a priori, de la composition du substrat. Son domaine d'application concerne donc l'analyse ponctuelle et l'acquisition d'images par spectroscopies Auger et d'émission X avec une mention particulière pour l'acquisition des profils en z par AES et l'analyse des revêtements superficiels en EDS EPMA. Les prédictions déduites de l'expression proposée sont en excellent accord (au moins pour Uo ≥ 3) avec les valeurs purement numériques déduites de simulations de Monte Carlo ou des solutions de l'équation de transport proposées par d'autres auteurs. Certaines incidences concernant l'influence de la rugosité de surface sur les mesures sont aussi évoquées

The Role of the Auger Mechanism in the Radiation Damage of Insulators

The ionization damage associated with electron and X-ray irradiation of insulating specimens during their investigation by various techniques (EM, AES, XPS, etc.) is considered from the point of view of the Auger mechanism. This damage results from the Auger electron transport through the specimen and more specifically from the Auger cascade in the excited atom. After electronic rearrangements, this cascade finally leaves elctron vacancies in the uppermost allowed states of the valence band. It is shown that these vacancies may explain various experimental results, such as the valent crystals. A possible way to quantify these effects is shown for the case of X-ray irradiation and for the case of electron irradiation. In the two cases, the correlation between microscopic mechanisms and their macroscopic consequences, from the point of view of charging effects, is pointed out for the first time. Finallyvarious positive aspects of these effects are outlined. They concern some new methods of characterization and of elaboration in materials science

Porte-échantillon ultra-vide à trois translations et trois rotations pour diffraction d'électrons

L'appareil décrit permet de communiquer de l'extérieur trois mouvements de translation et trois mouvements de rotation à un échantillon situé dans une enceinte ultra-vide. Il est actuellement utilisé comme porte-objet dans un appareil de diffraction d'électrons et, dans le cas des mesures par transmission, plusieurs objets peuvent être étudiés successivement

Backscattered electron imaging at low emerging angles: a physical approach to contrast in LVSEM

Due to the influence of refraction effects on the escape probability of the Back-Scattered Electrons (BSE), an expression of the fraction of these BSE is given as a function of the beam energy, E°, and emission angle (with respect to the normal) α. It has been shown that these effects are very sensitive to a local change of the work function in particular for low emerging angles. This sensitivity suggests a new type of contrast in Low Voltage Scanning Electron Microscopy (LVSEM for E°<2. keV): the work function contrast. Involving the change of φ with crystalline orientation, this possibility is supported by a new interpretation of a few published images. Some other correlated contrasts are also suggested. These are topographical contrasts or contrasts due to subsurface particles and cracks. Practical considerations of the detection system and its optimization are indicated

Optimisation du profil de dopage d'un MESFET réalisé par implantation ionique

On analyse l'interdépendance entre les performances d'un transistor à effet de champ en arséniure de gallium et son profil de dopage réalisé par implantation ionique. On étudie en particulier l'influence des conditions d'implantation (énergie et dose implantées) ainsi que celle du creusement de grille (« recess ») préalablement à la réalisation de la barrière Schottky. Les résùltats théoriques ont été obtenus à l'aide d'un simulateur permettant d'accéder aux propriétés statiques et dynamiques petits signaux du transistor à effet de champ pour tout profil de dopage non uniforme. Le temps de calcul a été réduit au maximum en associant des techniques analytiques et numériques. Le fonctionnement général du logiciel ainsi que les principes du calcul de toutes les caractéristiques électriques du composant sont détaillés. Les résultats de la simulation sont comparés aux résultats expérimentaux obtenus sur des structures réalisées en faisant varier les conditions d'implantation et la profondeur du creusement de grille. Enfin, l'influence du profil de dopage sur chacun des éléments du schéma équivalent du transistor à effet de champ GaAs est discutée en vue d'une optimisation des performances micro-ondes